Interpretation of measured gravity anomalies by 2D-modeling

Two dimensional gravity modeling is used frequently to estimate the possible sources, which cause a measured gravity profile (= anomaly):

Geological subsurface structures are simulated through closed polygons, which delimit different areas of constant densities. The gravity, which is calculated from this simulated underground situation, is compared to the measured gravity profile. By means of modification of the model the calculated gravity has to be adjusted to the measured one.

If both curves coincide within a certain error, we found one of the possible interpretations of the measured gravity.

Exercise:
Try to find a solution for the measured gravity profile (Sedimentary basin), which is marked by a blue line.

Observe the reaction of the calculated gravity (red line) on different depths of the body:
Near the surface, anomalies are strong and narrow, while deep seated bodies cause wide and smooth anomalies.

Modify the density: This changes only the amplitude of the anomaly, not its shape (wavelength).

Try to find several (ev. completely different?) solutions. Is it possible?
Which kind of modeling result can you derive definitely?
Which kind of modeling result would be more or less weak?
Interprete your model in terms of geology: Did you construct a model, which simulates a realistic geological situation?

Sorry - here you should see a Java Applet - you should install Java.....

Possible interactions:

Shift vertices Select and drag with left mouse button - the vertices are marked by a circle.

Delete vertices Move a vertex onto a direct neighbour.

Insert a vertex Click on a polygon side.

Change density Select a body by clicking into the corresponding polygon. Then either use the numerical input, or use the slider.
Densities are in kg/m³!

Add a body Activate the Button "Add new body", then input of at least three new vertices in clockwise order. Activate the button "Stop adding new vertices" to go back into normal mode.
To combine the new body with an existing body, select already existing vertices.

Zoom Click on the border of the model window, then move the cursor, or
Use SHIFT and left mouse button to change the scale, or
Use CTRL and left mouse button to change the position of the window

Possible interactions:
Shift vertices	Select and drag with left mouse button - the vertices are marked by a circle.
Delete vertices	Move a vertex onto a direct neighbour.
Insert a vertex	Click on a polygon side.
Change density	Select a body by clicking into the corresponding polygon. Then either use the numerical input, or use the slider. Densities are in kg/m³!
Add a body	Activate the Button "Add new body", then input of at least three new vertices in clockwise order. Activate the button "Stop adding new vertices" to go back into normal mode. To combine the new body with an existing body, select already existing vertices.
Zoom	Click on the border of the model window, then move the cursor, or Use SHIFT and left mouse button to change the scale, or Use CTRL and left mouse button to change the position of the window